The invention relates to a building sheeting with polymeric bitumen for construction purposes and a method of its manufacture.
Building sheetings with and without reinforcing carrier based on bitumen modified with polymers are known. Elastomers and polyolefins in particular are used as polymer. In practice, building sheetings with SBS (styrene-butadiene-styrene) or APP (atactic polypropylene) have gained acceptance. Both polymers bring about broadening of the plasticity span. SBS-modified bituminous building sheeting can be built in, for example, in the pouring method with blown bitumen, or can be furnished self-adherent; however, they are rendered sensitive to UV radiation and therefore as external building sheeting, they must be provided with a protective layer. Bituminous sheeting modified with APP cannot be attached with oxidized bitumen nor with elastomer contact adhesives.
APP-modified polymer sheetings exhibit inferior flexibility at low temperatures. In order to prevent this, an ethylene-propylene copolymerizate is frequently added. However, the surface of such bituminous building sheetings becomes tacky as a result of oily components exuding from the mixture so that sticking during storage results if the sheetings are not covered. In order to prevent this, DE-OS 19 41 630 suggests that up to 10% by weight sulfur be added to the bituminous mass. However, H.sub.2 S is produced during processing, which makes an expensive purification of exhaust gas necessary.
The migration of the oily components is also a reason for the poor compatibility with adhesive bitumen. An adhesion over the entire area and a combining of the overlapping seams with adhesive bitumen, e.g. according to the pouring method, is therefore not possible. The use of solvent-containing cold adhesives is also excluded on account of the sensitivity to solvents (lecture of N. A. Hendriks: Polymer-Bitumen Roof Sheeting, its Quality and Processing Properties; anniversary of the VEDAG-Koln, 1986). Therefore, APP-bitumen building sheetings are marketed exclusively as torching sheets (brochure, Homo-Plast Company for Homogeneous Insulation--and Sealing Technology mbH). The sheets are frequently covered on both sides with plastic films or provided on one side with a mineral dispersion.
In order to prevent the migration, the use of IPP (isotactic polypropylene) has been suggested as modifying agent for bituminous roofing material. However, these materials tend to dehomogenize in a hot state. Even when the cooling is very rapid, a very coarse structure is obtained which corresponds to a bitumen-filler-system and hardly changes the bitumen properties.
There was therefore the problem of developing building sheeting of the above-mentioned type with polypropylene-modified, bituminous covering materials which are compatible both with adhesive bitumen and with bituminous, cold, self-adhesive compositions.